The Reduction of the Electron Abundance during the Pre‐explosion Simmering in White Dwarf Supernovae

Chamulak, David A.; Brown, Edward F.; Timmes, F. X.; Dupczak, K.

doi:10.1086/528944

Cited by 81 publications

(133 citation statements)

References 55 publications

(110 reference statements)

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“…However, the progenitor is expected to develop a neutron excess before flame ignition both during the CNO and He burning cycles and during a ∼1000 yr epoch of hydrostatic carbon burning which is sometimes referred to as "simmering." Recent studies of the "simmering" epoch indicate that when carbon burning runs away locally and a flame is born, η sim ≈ 10 −3 (Piro & Bildsten 2008;Chamulak et al 2008) in stars with zero metallicity, while stars with an initial metallicity comparable to solar will develop a neutron excess of η ≈ 1.5 × 10 −3 by the time core He burning commences.…”

Section: Iron-peak Freeze-out Yields: Resultsmentioning

confidence: 99%

STUDY OF THE DETONATION PHASE IN THE GRAVITATIONALLY CONFINED DETONATION MODEL OF TYPE Ia SUPERNOVAE

Meakin

Seitenzahl

Townsley

et al. 2009

ApJ

100

118

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We study the gravitationally confined detonation (GCD) model of Type Ia supernovae (SNe Ia) through the detonation phase and into homologous expansion. In the GCD model, a detonation is triggered by the surface flow due to single-point, off-center flame ignition in carbon-oxygen white dwarfs (WDs). The simulations are unique in terms of the degree to which nonidealized physics is used to treat the reactive flow, including weak reaction rates and a time-dependent treatment of material in nuclear statistical equilibrium (NSE). Careful attention is paid to accurately calculating the final composition of material which is burned to NSE and frozen out in the rapid expansion following the passage of a detonation wave over the high-density core of the WD; and an efficient method for nucleosynthesis postprocessing is developed which obviates the need for costly network calculations along tracer particle thermodynamic trajectories. Observational diagnostics are presented for the explosion models, including abundance stratifications and integrated yields. We find that for all of the ignition conditions studied here a self-regulating process comprised of neutronization and stellar expansion results in final 56 Ni masses of ∼1.1 M . But, more energetic models result in larger total NSE and stable Fe-peak yields. The total yield of intermediate mass elements is ∼ 0.1 M and the explosion energies are all around 1.5 × 10 51 erg. The explosion models are briefly compared to the inferred properties of recent SN Ia observations. The potential for surface detonation models to produce lower-luminosity (lower 56 Ni mass) SNe is discussed.

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Section: Iron-peak Freeze-out Yields: Resultsmentioning

confidence: 99%

STUDY OF THE DETONATION PHASE IN THE GRAVITATIONALLY CONFINED DETONATION MODEL OF TYPE Ia SUPERNOVAE

Meakin

Seitenzahl

Townsley

et al. 2009

ApJ

100

118

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“…0.43 protons per reaction, gives 0.14 electron captures for every 12 C nuclei consumed in the above chains. At densities in excess of 10 9 g cm −3 , other electron captures become energetically feasible and the ratio of electron captures per 12 C nuclei destroyed increases to a typical value of ∼0.3 (Chamulak et al 2008). On the other hand, a proton yield as low as that found by S07 for the 2.14 MeV resonance can modify substantially the ratio of electron captures per 12 C nuclei destroyed.…”

Section: Neutronization During Carbon Simmeringmentioning

confidence: 91%

“…Timmes et al (2003) proposed a linear relationship between the mass of 56 Ni and metallicity: M( 56 Ni) ∝ 1 − 0.057Z/Z . Later, Chamulak et al (2008) argued that even a zero metallicity progenitor is subject A114, page 8 of 15 to neutronization through electron captures during the time that elapses between the crossing of the carbon ignition curve and the onset of the dynamical event, i.e. until the timescale becomes on the order of 1-10 s. The neutronization during the simmering phase would affect mainly SNIa from low metallicity progenitors, and the relationship between M( 56 Ni) and Z would change slightly, to become M( 56 Ni) ∝ 0.965 − 0.057Z/Z .…”

Section: Neutronization During Carbon Simmeringmentioning

confidence: 98%

“…In general, the thermal timescale is shorter than the nuclear timescale by a factor τ th /τ nuc 2c p T/QN A Y 12 , where c p is the specific heat at constant pressure and Q is the effective heat release per carbon fusion reaction, Q 9.1 MeV (Chamulak et al 2008). For instance, at T = 6 × 10 8 K, τ th /τ nuc 0.06 but, owing to the steep slope of the τ nuc vs. T curves (see Fig.…”

Section: Low-energy Resonancementioning

confidence: 99%

“…The third factor, namely the number and distribution of runaway centers, also known as hot spots or igniting bubbles, is intrinsically multidimensional, so that it cannot be determined with our onedimensional hydrostatic code. Hence, we consider alternative ways of addressing both the dependence of the neutronization during carbon simmering (Chamulak et al 2008;Piro & Bildsten 2008) and the number and distribution of hot spots, on the presence of a LER in the 12 C+ 12 C reaction (Woosley et al 2004). …”

Section: Physical Conditions At Thermal Runawaymentioning

confidence: 99%

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Type Ia supernovae and the¹²C+¹²C reaction rate

Bravo

Piersanti

Domínguez

et al. 2011

A&A

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Context. Even if the 12 C+ 12 C reaction plays a central role in the ignition of type Ia supernovae (SNIa), the experimental determination of its cross-section at astrophysically relevant energies (E 2 MeV) has never been made. The profusion of resonances throughout the measured energy range has led to speculation that there is an unknown resonance at E 0 ∼ 1.5 MeV possibly as strong as the one measured for the resonance at 2.14 MeV, i.e. (ωγ) R = 0.13 meV. Aims. We study the implications that such a resonance would have for our knowledge of the physics of SNIa, paying special attention to the phases that go from the crossing of the ignition curve to the dynamical event.Methods. We use one-dimensional hydrostatic and hydrodynamic codes to follow the evolution of accreting white dwarfs until they grow close to the Chandrasekhar mass and explode as SNIa. In our simulations, we account for a low-energy resonance by exploring the parameter space allowed by experimental data. Results. A change in the 12 C+ 12 C rate similar to the one explored here would have profound consequences for the physical conditions in the SNIa explosion, namely the central density, neutronization, thermal profile, mass of the convective core, location of the runaway hot spot, or time elapsed since crossing the ignition curve. For instance, with the largest resonance strength we use, the time elapsed since crossing the ignition curve to the supernova event is shorter by a factor ten than for models using the standard rate of 12 C+ 12 C, and the runaway temperature is reduced from ∼8.14 × 10 8 K to ∼4.26 × 10 8 K. On the other hand, a resonance at 1.5 MeV, with a strength ten thousand times smaller than the one measured at 2.14 MeV, but with an α/p yield ratio substantially different from 1 would have a sizeable impact on the degree of neutronization of matter during carbon simmering. Conclusions. A robust understanding of the links between SNIa properties and their progenitors will not be attained until the 12 C+ 12 C reaction rate is measured at energies ∼1.5 MeV.

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Nucleosynthesis in Thermonuclear Supernovae

Seitenzahl¹,

Townsley²

2017

Handbook of Supernovae

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The explosion energy of thermonuclear (Type Ia) supernovae is derived from the difference in nuclear binding energy liberated in the explosive fusion of light "fuel" nuclei, predominantly carbon and oxygen, into more tightly bound nuclear "ash" dominated by iron and silicon group elements. The very same explosive thermonuclear fusion event is also one of the major processes contributing to the nucleosynthesis of the heavy elements, in particular the iron-group elements. For example, most of the iron and manganese in the Sun and its planetary system was produced in thermonuclear supernovae. Here, we review the physics of explosive thermonuclear burning in carbon-oxygen white dwarf material and the methodologies utilized in calculating predicted nucleosynthesis from hydrodynamic explosion models. While the dominant explosion scenario remains unclear, many aspects of the nuclear combustion and nucleosynthesis are common to all models and must occur in some form in order to produce the observed yields. We summarize the predicted nucleosynthetic yields for existing explosions models, placing particular emphasis on characteristic differences in the nucleosynthetic signatures of the different suggested scenarios leading to Type Ia supernovae. Following this, we discuss how these signatures compare with observations of several individual supernovae, remnants, and the composition of material in our Galaxy and galaxy clusters.

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The Reduction of the Electron Abundance during the Pre‐explosion Simmering in White Dwarf Supernovae

Cited by 81 publications

References 55 publications

STUDY OF THE DETONATION PHASE IN THE GRAVITATIONALLY CONFINED DETONATION MODEL OF TYPE Ia SUPERNOVAE

STUDY OF THE DETONATION PHASE IN THE GRAVITATIONALLY CONFINED DETONATION MODEL OF TYPE Ia SUPERNOVAE

Type Ia supernovae and the¹²C+¹²C reaction rate

Nucleosynthesis in Thermonuclear Supernovae

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The Reduction of the Electron Abundance during the Pre‐explosion Simmering in White Dwarf Supernovae

Cited by 81 publications

References 55 publications

STUDY OF THE DETONATION PHASE IN THE GRAVITATIONALLY CONFINED DETONATION MODEL OF TYPE Ia SUPERNOVAE

STUDY OF THE DETONATION PHASE IN THE GRAVITATIONALLY CONFINED DETONATION MODEL OF TYPE Ia SUPERNOVAE

Type Ia supernovae and the12C+12C reaction rate

Nucleosynthesis in Thermonuclear Supernovae

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Product

Resources

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Type Ia supernovae and the¹²C+¹²C reaction rate